This invention relates generally to the art of grinding and more particularly to a process and apparatus for automatically and reproducibly grinding a desired configuration from a elongated blank.
In the prior art various manual and some automatic techniques have been developed for the production of machined articles. Such machined articles are of various sizes and shapes and can be of the size of a turpine rotary down to the size of a denist drill of even smaller. For purposes of this disclosure the term "bur" is utilized as descriptive of the product produced by the prior art and of the machined article produced by the invention which is described below. However, the method and apparatus of this invention are applicable to all sizes of machined articles which are produced from elongated blanks.
A bur is a cutting or grinding tool. Small burs are commonly used in densitry as the major cutting tool for grinding or drilling teeth. Larger burs are used in a variety of manufacturing operations. Most of the time, the bur is used as a grinding tool for the removal of excess material after casting of machining processes. In general, the bur is used in a hand held operation. As a result, the precise shape of the bur is not usually critical. The bur is sometimes called a rotary file. For many years the bur has been manufactured from tool steel, but as the speed of the grinding tools has increased it has been recognized that tungsten carbide provides superior wear properties. Thus the demand for tungsten carbide tools has increased.
Blanks of cast tungsten carbide are ground with a metal based, diamond impregnated wheel to produce a bur with the desired shape and cutting characteristics. Burs are manufactured in a wide variety of sizes and shapes with special flute configurations for various applications. FIG. 1 illustrates some of the variety of shapes that are available for burs. Bur shapes are generally standardized. The normmal process for the production of tungsten carbide burs is for skilled craftsmen to use a diamond grinding wheel to hand grind the blanks into the desired shapes and flute patterns.
It is partially due to the number of different combinations of bur flute configurations that it has been difficult to utilize machines to replace the human craftsman in the bur manufacturing process. The use of skilled operators to produce burs leaves little opportunity for significant reductions in the cost of production. In addition, regardless of the skill of the operator, it has not been possible to precisely control the quality of the burs. In order to improve the productivity and quality of burs, several mechanical and computer controlled machines have been developed that are capable of partial automation. However, to date, the standard for comparison for the production of burs is the handmade bur.
Shapes of the burs have been sufficiently standardized that the American National Standards Institute (ANSI) has developed a set of standards for the "Blanks for Carbide Burs" (ANSI B94.13-1976) which defines the nominal dimensions and geometries of blanks that can be used in the production of tungsten carbide burs. These standards are hereby incorporated by reference.